I have 3 completely different lines that I cross back and forth and every so often I bring in new genetics to keep things fresh.
I don't breed brothers and sisters but have bred offspring back to parents a few times.

Your rats look like it has a rex coat, the whiskers seem to straight to be a hairless rats.

You say the mom was a standard coat, do you know what the daddy rat was?
I frequently breed double rex coat rats to standard coat rats so I can have full litters of rex coats, maybe the dad rat was a double rex?